Maintaining the temperature of an object under a given set of environmental conditions may be difficult to achieve. Such temperature stability involves maintaining warm objects at a warm temperature and cold objects at a cold temperature. Further, temperature stability should be achieved efficiently and cost-effectively.
Temperature stability is desirable in a broad range of environments and situations. These include, for example and without limitation:    1) Keeping an individual, such as an airplane mechanic, comfortable and productive while working outdoors in cold winter weather or in hot summer weather;    2) Keeping an individual, such as a soldier or an airline passenger, comfortable during flight on an aircraft;    3) Keeping an engine or battery warm during a shutdown operation; and    4) Keeping an object, such as a roll of composite pre-preg, cold before use.
Generally stated, people and objects gain or lose heat through four mechanisms: conduction, convection, evaporation, and radiation. Approaches to maintain temperature stability often address one or more of these four mechanisms, and include, for example, without limitation:                1) Use of a convection heater, forced air heater, or air conditioner. These produce a stream of hot or cold air and reduce losses occurring through conduction and convection.        2) Use of insulation. This includes blankets of insulation on machines or in building walls, and can include a coat or mittens worn by people. This approach reduces losses occurring through conduction, convection, and, in some cases, radiation.        3) Shade. Whether natural or artificial, this blocks a source of radiant heat.        4) Use of a radiant heater. This produces radiant heat—typically infrared—and therefore heats by radiation.        5) Use of a “space blanket” or reflective insulation. When wrapped around a person or object, these reflect some of the infrared energy emitted by the person or object back to them. However, unless the insulation completely surrounds the person or object, the infrared reflection is minimally effective and most of the infrared energy is lost to the environment. Multilayer insulation (MLI) used on spacecraft is an example.        6) Combinations of the above. For example, jackets that contain battery-powered heaters or that include a reflective layer that utilizes specular reflection to return heat to the wearer.        
There are instances in which wrapping a person or object with adequate insulation is not practical. Such cases include, for example:                1) An individual, such as a mechanic, working in cold weather but needing to use their fingers for fine work;        2) An individual, such as a mechanic, in cold weather having a repeated need to reach overhead in order to work, where the weight of a heavy coat would impede their ability to reach workpieces or otherwise cause repetitive stress injury;        3) An office worker in a cold office who needs their fingers free to type, as well as the need to be able to execute other fine motor skills; and        4) Machinery or material that must not get too cold in winter or too hot in sunlight while still allowing access for people to work on it.        
Active heating/cooling systems are likewise not practical or optimal in many instances. For example, it may be necessary to place such systems very close to the individuals and objects to maintain their temperature stability. This limits the mobility of the individual and/or the accessibility or portability of the object.